International Journal of Geomechanics

For many aspects of rock engineering, it is important to measure the in situ stresses, not only under compression but also under tension. Brazilian tests were performed to generate tensile stress in granite samples. The granite was obtained from the Beishan site, a potential high-level radioactive waste repository area in China. In this study, Brazilian testing was performed on the Beishan granite samples via cyclic loading, increasing the magnitude of the stress either every cycle or every other cycle. This allowed for assessment of the Kaiser effect method’s reliability in evaluating the tensile stress of a sample. The experimental results confirm the existence of the Kaiser effect in rocks under tensile stress. The Kaiser effect was obvious when the pre-existing stress was smaller than the crack damage stress and was ambiguous when the pre-existing stress exceeded the crack damage stress, after which cracks began to propagate and coalesce in an unstable manner. The felicity ratio values associated with the stress and mechanical parameters consistently decreased with increasing pre-existing stress.

The new generation of wide-base tires and the traditional dual-tire assembly are the main types of tire configurations used in the drive and trailing axles of trucks. However, the response of pavement to these configurations is not the same. Wide-base tires have more detrimental effects on pavement performance and less impact on the environment. The use of geosynthetics for reinforcing can improve the pavement performance against the detrimental effects of tires and prevent the occurrence of premature distresses. This research attempted to compare the performance of geogrid-reinforced and unreinforced pavement under both wide-base and dual-tire configurations by determining some of the critical responses of the pavement types. Viscoelastic analysis was conducted using the three-dimensional (3D) finite-element method in Abaqus software. A typical flexible pavement structure in Iran was used in all analyses. One type of high-modulus geogrid was used at the bottom of the asphaltic layer for reinforcement. Moreover, the distribution of the longitudinal and transverse tensile strains and the vertical shear strains throughout the thickness of asphaltic layer was determined. Results showed that, in general, under the same axle load, the single wide-base tire induced considerably higher strains than the dual tires. It was also found that under the same conditions, the maximum transverse tensile strain under the wide-base tire was approximately twice that under the dual-tire configuration. In addition, the results revealed that under dual tires, the distribution of the stains throughout the depth of the asphaltic layer was more uniform than that under the wide-base tire. It was also found that the geogrid reinforcement was significantly effective in reducing the critical strains. However, the reinforcement was observed to be more effective in reducing the tensile strains than the shear strains.

Potentially, a seabed may be characterized rapidly and economically by using dynamically installed free-falling penetrometers (FFPs). Because of their relatively rapid deployment and recovery, FFPs may be preferred over conventional full-flow or cone penetrometers for characterizing seabeds. However, despite several successful field trials of FFPs, significant uncertainty still exists about the data interpretation, mainly because of the fast nature of the penetration process, during which regions of the soil body close to the penetrometer experience very high strain rates. The consequence of such high strain rates on pore pressure measurement is not well known. Furthermore, the rigorous numerical analysis of the problem is notoriously difficult because it involves large deformations, dynamics, hydrodynamic coupling, highly nonlinear material behavior, rate dependency, and contact mechanics. A finite-element procedure was developed and used in this study to provide a dynamic coupled solution for the penetrometer impact and burial into saturated clay. Subsequently, some mechanisms involved in the generation of excess pore pressures were investigated with specific attention given to the effects of the penetrometer tip geometry and the location of the pore pressure measuring devices. An important numerical challenge in modeling this problem is highlighted in this paper. It concerns the numerical diffusion that can occur because of the remeshing process required in this large deformation, moving boundary problem.

This article examines the response of soil slopes under adjacent embedded strip foundations, subjected to increasing vertical load due to the gravity load of buildings. The study also considers slopes under closely spaced adjacent buildings. In addition, the article addresses the effects of horizontal earthquake loading using the simplified pseudostatic method. The response of two representative slopes was investigated using nonlinear two-dimensional finite element limit analysis with a strength reduction method. The effects of interaction between building, foundation, and slope on the sliding surface, factor of safety (FOS), and ultimate load intensity (ULI) were explored. Furthermore, the effects of integral action of building frame on slope-building interaction were investigated. It was found that the buildings/foundations mostly result in local failure of stable slopes under gravity and seismic loads. Consequently, the slope's FOS was found to be sensitive to foundation loading intensity, but in most of the considered cases it was insensitive to the number and distance between adjacent foundations and buildings.

The evaluation of the failure mechanism of a shallow tunnel is very significant in geotechnical engineering. In this literature an analytical methodology for determining the plane strain limit failure mechanism for a shallow tunnel with an arbitrary cross section is presented. The paper presents active and passive failure modes for the shallow tunnels in linear and nonlinear soils. By variation calculus, the effects of dilation on the failure mechanism of the shallow tunnel are explored based on the nonassociative flow rule in the present work. Within the upper bound theorem different curve functions are obtained to describe the different failure mechanisms up and down the water level. Good agreement is demonstrated in both active and passive failure mechanisms with the lower bound solution solved in the similar trapdoor/anchor problem in linear Mohr-Coulomb soils. To analyze the influence of the dilatancy coefficient and position of the water table on the potential failure range, some examples and sensitivity analysis are conducted, which shows great consistency with existing research findings.

Freezing in saturated saline soil is a dynamic, coupled hydraulic-thermal-salt-mechanical (HSTM) process. The aim of this paper is to establish a model to describe the coupling process. In the model, mass conservation law, Darcy’s law, and the energy conservation law are applied. The Clapeyron equation is used to illustrate the phase equilibrium in the multiphase system of soil, ice, and water, which contributes to the simplification of the soil-water potential. A freezing experiment using a 20-cm soil column with top-side freezing was performed, and the model was solved using transient finite elements. The numerical simulation fit well with the experiment data. The results show the temperature distribution, the water content distribution, the frost heave amount, and the salt distribution at different times along the one-dimensional column. In addition, it was found that the temperature in the frozen zone changes faster than that in the unfrozen zone, and the temperature distribution tends to be stable after freezing for 96 h, resulting in upward water migration toward the freezing front from the unfrozen zone and the formation of ice lenses. Because of the water migration, an expansion process is produced, and salt is transported upward constantly. Excess salt is precipitated if the solute concentration exceeds the solubility. These results provide a reference for soil salinization and frost heave behavior in saline soils in cold regions.

Reinforcements are essential for improvement of slope stability. In most slope stability analyses, the soil is regarded as homogeneous, whereas it is in fact nonhomogeneous in many cases. Based on the limit-analysis method, in this study, a three-dimensional seismic and static stability calculation was performed for a slope in nonhomogeneous soil. The analytical expressions of the required strength of reinforcement and stability factor under three categories of reinforcement patterns were derived. The effects of reinforcement distribution patterns, reinforcement strength, slope angle, seismic force, and soil nonhomogeneity and anisotropy on slope stability were investigated. It was found that the downwardly strong triangular distribution pattern (DTD) gives rise to the best reinforcement effect on slope stability, then the uniform distribution pattern (UD), and finally the upwardly strong triangular distribution pattern (UTD). An increase in the angle and width of the slope and seismic forces results in a stability decrease of the reinforced slope, whereas soil nonhomogeneity and anisotropy have positive influences on slope stability. Finally, some design tables are presented for design purposes.

A simplified numerical procedure to model a deep-penetration process, press-replace method (PRM), was used to simulate a cone penetration test (CPT) in undrained conditions with finite-element software. A detailed description is given on how PRM can be implemented in CPT. The performance of PRM was validated by comparing results obtained with solutions from three other numerical approaches: large-deformation finite element (LDFE), steady-state finite element (SSFE), and material point method (MPM). For a wide range of soil rigidities, initial soil stress anisotropy and roughness conditions, normalized cone factors from PRM using a Tresca model, agreed within 10% of LDFE, and the average value was greater than LDFE by 4%. Total stress, principal stress directions, and magnitudes from PRM were also found to be similar to LDFE results. The PRM approach was then applied to a modified Cam-clay soil model. Excess pore-pressure distributions calculated around the cone agreed well with solutions by SSFE. For a smooth cone with various initial stress states, PRM calculated cone tip resistances that were approximately 7% more than MPM.

The mechanical properties and anchorage performances of rock masses are important to the success of underground engineering in fault fracture zones, but the impact of the rock block size and cementing strength on these properties and performances is unclear. A set of laboratory methods was developed to simulate the development of rock masses in fault fracture zones. Next, model specimens were prepared from natural rock blocks of different sizes and cementing materials of various strengths, and an aluminum alloy bar was installed as a model bolt to fabricate anchored model specimens. Compared with natural rock samples, the fault fracture rock mass exhibited a clear degradation in its strength and deformation parameters, and the degradation coefficients ranged from 19.20 to 86.51%. Under an applied axial load, as the rock block size or cementing strength increased, the mechanical parameters, including peak strength and elastic modulus, for both anchored and nonanchored model specimens increased from 16.90 to 69.05%. Because of the anchorage performance of the bolt, the anchored model specimens presented larger mechanical parameters than those of the nonanchored models. The effective anchorage strength of the bolt was found to be generally stable as the rock block size increased, but it decreased with the cementing strength. The ultimate failure modes of the anchored models with smaller aggregate sizes or lower cementing strengths were found to be characterized by cracks propagating along the cementing surface. For models with a larger rock block size or higher cementing strength, crack development throughout the intact rock blocks was also observed.

Prediction of soil displacements adjacent to braced excavations is critically important, especially in urban areas, to prevent any potential damage of adjacent buildings, service lines, and other infrastructure facilities. In the present study, a new theoretical approach was proposed for estimation of ground deformation and wall deflection at any section within the influence zone of braced excavation, considering soil deposit as a three-dimensional elastic continuum. The principle of minimum potential energy was applied to obtain the governing differential equation for both horizontal and vertical displacements in the continuum. A flowchart of design procedure was presented in which soil parameters λ and G (Lame’s constants) were incorporated to characterize soil deformation. For proper linkage between horizontal and vertical soil movements, soil displacement profiles at various locations around excavation were assumed. The computed results were compared with the observed values obtained from three different case studies in which excavations were performed mainly in soft to medium clays. The present study showed that the proposed method predicts well for different field conditions and can be used as a simplified approach to obtain ground and wall deformations at various depths and horizontal distances.

In this study, the stability of twin circular tunnels in purely cohesive and cohesive-frictional soils was evaluated. It is assumed that the internal compressive normal pressure (σ_i) required to support the tunnels, by means of lining and the anchorage system, becomes uniform (isotropic) on the tunnels' periphery. The interference effect of twin tunnels on the magnitude of σ_i was examined by employing upper-bound limit analysis in conjunction with finite elements and linear optimization. The internal support pressure (σ_i) needed to maintain the stability of the tunnels is expressed in the form of a dimensionless parameter (σ_i/c), which becomes a function of the dimensionless variables S/D, H/D, γD/c, ϕ, and m, where c refers to soil cohesion, S is the clear spacing between the tunnels, H implies tunnel cover, D corresponds to diameter of each tunnel, ϕ is the internal friction angle of soil mass, and m accounts for the rate at which the cohesion increases linearly with depth. The effect of the changes in S/D on the magnitude of σ_i/c was examined for different combinations of H/D, γD/c, m, and ϕ. The results are presented in the form of nondimensional stability charts that can be readily employed by practicing engineers for the purpose of design.

This study incorporated an elastic brittle damage constitutive model into a program for modeling and analysis through a user subroutine interface to define a material’s mechanical behavior and considered nonlinear geometric effects. The Weibull distribution function was adopted to consider the heterogeneity-related uncertainty of the strength and stiffness. The 2D models used were discretized using plain strain reduced integration elements with the option of element removal after being fully damaged. We verified the accuracy of the user subroutine code by reproducing the observed failure behavior of an intact sandstone specimen with using previously suggested material parameters. The reliability of the numerical model was supported by an agreement between pre-existing experimental results and the numerical simulation results for specimens containing a single fissure with different inclination angles. Two parametric studies were conducted on the failure behavior of a specimen with a single fissure to investigate the effect of (1) the heterogeneity level and (2) the confining pressure. Stiffness and strength were shown to decrease with increases in the level of heterogeneity. Tensile cracks that appeared in the more homogeneous models were replaced by scattered damaged elements with increasing heterogeneity. Increasing the confining pressure increased the load capacity of the specimen, regardless of the inclination of the fissure angle. This trend was related to the amount of damage occurring before reaching the peak load. The maximum load was typically lower when the route length of the cracks formed before the peak load was larger. To investigate fracture coalescence behavior, specimens with two parallel fissures were modelled for four different ligament angles. The numerical simulations agree with the available experimental results, indicating that coalescence changed from shear to a tensile mode as the ligament angle increased.

The stability of shallow, artificial underground cavities in soft rocks interacting with overlying structures and infrastructures represents a challenging problem to be faced. This paper discusses a methodology that can be useful for a preliminary stability assessment of underground cavities in soft calcarenites based upon the results of parametric two-dimensional (2D) and three-dimensional (3D) finite-element analyses of ideal underground cavities. The study aimed at exploring those relationships between the geometrical parameters of the cave system and the strength properties of the rock material to define charts that can be useful to evaluate the stability of the rock mass. Moreover, the influence of three-dimensionality was also accounted for based on 3D parametric analyses with variable cavity length and the comparison with the results of the corresponding 2D analyses.

Anaerobic–aerobic hybrid bioreactor landfills, operated in a specific way that combines the benefits afforded by both anaerobic and aerobic processes, can significantly enhance the degradation of municipal solid waste (MSW) and the recovery of energy. The present article describes an application of computational fluid dynamics (CFD) to the numerical simulation of subsurface leachate recirculation and aeration systems in hybrid bioreactor landfills. The objective of the study was to model and investigate the hydrodynamic and biochemical behavior within a hybrid bioreactor landfill. The results indicate that the suitable transition time that ensures that the most methane potential has been exploited and that the hybrid landfill changes to aerobic conditions to shorten the stabilization process effectively is when 70–80% of methane potential has been exploited. A relatively small injection pressure is suggested in the initial stage of aeration for MSW with small permeability, and the injection pressure can be raised after the pore pressure dissipates and leachate flows out of landfills smoothly. Results also show that a reasonable method of intermittent leachate recirculation during aeration is to start it when the water content decreases to the minimum value required for the hydrolysis reaction and stop it once the maximum hydrolysis rate is reached and that the configuration of the group-well system has an obvious effect on the leachate volume, whereas it appears to have a relatively small effect on the air volume.

Major offshore and onshore structures, including transport corridors and high-rise buildings, resting on soft compressible clays are often supported by pile foundations. Apart from the usual vertical loading from the superstructures, these piles are usually subjected to large cyclic loads arising from the actions of waves, ship impacts, or moving vehicles. Under such circumstances, vertical and lateral modes of cyclic loading are predominant and affect overall stability. Such repetitive loading on piles leads to reversal of axial stresses in the adjacent soft clay, initiating progressive degradation in soil strength and stiffness that deteriorates the pile capacity with unacceptable displacements. Although several studies have been carried out to investigate the response of a single pile, a detailed investigation on a pile group in soft soil subjected to cyclic lateral loading, which is of immense practical interest to field engineers, had yet to be conducted. In this paper, extensive laboratory model tests with steel-pipe-pile groups in soft cohesive soil were conducted followed by the development of a numerical model that was based on a two-dimensional (2D) dynamic finite-element (FE) approach. The degradation of both axial and lateral capacities of the pile group and the pattern of the degradation with variations in the cyclic-loading parameters were studied. Comparisons of the experimental data with the computed results validated the numerical analysis. The study indicates that both the axial and lateral pile capacities and displacements were significantly influenced by the cyclic-loading parameters (number of cycles, frequency, and amplitude). Relevant design recommendations are presented.

Current research to predict the soil deformation due to tunneling pays little attention to the impact of soil–liner interaction. Moreover, the conventional solution for the stress function method has an inherent physical defect that leads to a nonzero ground displacement at infinity. To overcome these disadvantages, an analytical solution by the complex variable method is presented for problems in evaluating the liner and disturbed surrounding soil deformation due to tunneling in clays. The interaction mechanism between tunnel liners and surrounding soils is considered in this study, and the deterministic nonuniform convergence boundary model is composed as the displacement controlled condition on tunnel opening. The applicability of the proposed method is observed based on the existing analytical solutions and a series of field cases. It has been demonstrated that the proposed complex variable solution for the estimation of soil displacements considering the soil–liner interaction and nonuniform convergence model agrees well with the observation data. The impacts of key parameters on the tunneling-induced soil deformation are also assessed, including the tunneling gap, the soil and liner physical characteristics, and the buried depth liner thickness for the tunnel. In addition, the effects of the liner thickness and buried depth on the circular expression of liner deformation, including the radial and tangential displacements, are investigated by the parametric analyses considering the soil–liner interaction mechanism. To consider the liner stiffness influence and the nonuniform convergence boundary condition, the complex variable solution in this study can be regarded as an effective approach to conservatively predict the soil and liner deformation.

The grouting of a rock mass is frequently adopted in engineering to enhance the strength and integrity of jointed rock. Based on the principle of hydraulic fracturing, grouting slurry with high pressure is injected into the rock mass, resulting in the emergence and propagation of hydraulic fracture. In this work, a numerical model with cohesive finite elements was developed to simulate the grouting of a rock mass, which couples the stress-seepage-damage field. The model considers the fluid exchange between the porous, permeable medium and fractures, in addition to the coupling of fluid exchange and rock deformation. The effect of fluid lag on pore pressure in the vicinity of the fracture tip is specifically analyzed. Results show that the variation of pore pressure in the broken cohesive zone can be divided into four stages: the initial steady-wave stage, descending stage, sharp-rise stage, and fluctuation-rise stage. There is a significant region of lowered pore pressure in the vicinity of the fracture tip as a result of the effect of fluid lag.

In this paper, seismic bearing capacity factors for shallow strip foundations embedded in homogeneous c-ϕ soil slopes are presented. A numerical study is performed using finite-element limit analysis (FELA) with lower bound (LB), upper bound (UB), and 15-node (15N) mixed Gauss element formulations. The pseudostatic approach is used to consider the seismic action on both soil and foundation. The study explores the influence of different governing parameters, namely slope angle (β), angle of internal friction (ϕ), foundation embedment depth ratio (D/B, where D = depth of the footing from slope surface; and B = width), and horizontal seismic coefficient (α_h), on the ultimate bearing capacity of the embedded strip foundation. The bearing capacity factors N_cs and N_γqs decrease rapidly with an increase in β and α_h, and an increase with D. Compared with N_cs, the factor N_γqs is more sensitive to the changes in β, ϕ, D/B, and α_h. Based on the results obtained from the study, a set of design charts and a simple spreadsheet-based tool (SBCSFES) are developed.

This article presents nondimensional solutions for laterally loaded piles in sand considering nonlinear soil–pile interactions. A nonlinear elastoplastic p–y model, termed the H-model, is introduced, and its ability to model the responses of laterally loaded piles in sand is demonstrated. Nondimensional forms of both the H-model and the governing equation for laterally loaded piles are then derived, after which the nondimensional responses of free-head piles subject to lateral forces and moments and that of fixed-head piles subject to lateral forces are evaluated using the finite-element method. It is found that (1) the pile responses are significantly affected by the nondimensional pile length; and (2) using nonlinear soil–pile interaction, the critical length of the pile increases with increasing normalized displacement and is noticeably larger than that utilizing linear soil–pile interaction. The quantitative nondimensional relationship between force and the moment responses of free- and fixed-head long piles is also obtained. Two design curves, normalized force against normalized displacement and normalized force against maximum normalized moment, are presented. Illustrative examples are given to show the step-by-step procedure for how the curves could be used in practice to estimate the behavior of piles.

A large number of discontinuities is frequently encountered in geotechnical engineering that significantly influences the stability of engineering. Therefore, it is important to investigate the mechanical properties and failure modes of a flawed rock mass. For this study, a series of uniaxial compression experiments was carried out on yellow sandstone samples containing a single flaw and mechanical analyses were conducted accordingly. The experimental results suggested that hydraulic pressure can induce a relatively high peak axial strain in the samples. However, the hydraulic pressure had a different influence on the uniaxial compressive strength of samples with flaws at different inclination angles. Moreover, three new types of crack were observed: One was a tensile crack, and the others were lateral cracks that emerged in samples under hydraulic pressure. On the basis of the analytical method, the calculated results were verified by the experimental results. The findings indicated that the crack initiation position moved toward the flaw tip and the crack initiation angles were reduced when the hydraulic pressure acted on the flaw surface. Furthermore, the hydraulic pressure induced greater initiation strength and strain in the samples, except for the samples with inclination flaws greater than 75°.

This article presents particle breakage and the undrained shear behavior of sands, with the purpose of interpreting the undrained shear behavior of the precrushed sands by detecting the influence of particle breakage on the basis of the contractive stage, the dilative stage, and the whole shear stage of sand behavior. Particle breakage resulted in impairment of the dilatancy behavior of sand (or intensification of the contractancy behavior of sand) in influencing the stress–strain behavior of sand with intensification of the excess pore-water pressure. Under the same initial void ratio, the critical state was characterized by a reduction of the mean effective stress with increasing particle breakage in the e-logp′ plane. In view of all critical states on the same particle breakage, particle breakage resulted in the translation and rotation of the critical state line in the e-logp′ plane, but the critical state followed and evolved downward along the two-segment critical state line in the q–p′ plane with increasing particle breakage. In the q–p′ plane, particle breakage had an insignificant influence on the phase transformation line, but the phase transformation state evolved downward along the phase transformation line with increasing particle breakage. During each shear stage (the contractive stage, the dilative stage, or the whole shear stage), particle breakage resulted in movement of the confining-pressure normalized loci of the delta excess pore-water pressure ($\Delta u$) and delta deviator stress ($\Delta q$) $(\Delta u–\Delta q)$ and the delta excess pore-water pressure (Δu) and delta mean effective stress (${\Delta p}^{\prime }$) ($\Delta u$–${\Delta p}^{\prime })$ toward and then along a linear reference line with an increase of the normalized delta excess pore-water pressure and a decrease of the normalized delta deviator stress and the normalized delta mean effective stress with increasing particle breakage. In addition, the divergence from the linear reference line was revealed to decrease and even vanish with increasing confining pressure.

A soil-water retention curve (SWRC) is one of the important constitutive laws for soil-water distribution and shear-strength assessment in unsaturated soil. A SWRC commonly shows the hysteretic behavior under drying and wetting conditions. Several mathematical models have been developed to describe hysteresis, including a model commonly presented in the literature and implemented into HYDRUS software. Recently, the authors developed a new hydraulic hysteresis model for which only one additional parameter was introduced to capture the effects of capillary and air-entrapment hysteresis. To confirm the capabilities of the two models in analyzing the unsaturated flow, the authors’ model was implemented with a numerical code using the FORTRAN language. The numerical codes including the authors’ model and the model in HYDRUS for hysteresis assessment were used to analyze the same transient unsaturated flow problems under drying and wetting conditions. By comparing the measured data to curves predicted by the two models, the results show that the hysteretic SWRC cannot be described correctly when the effects of hydraulic hysteresis are ignored under drying and wetting conditions. Moreover, the comparison between the results predicted by the two models shows that the authors’ model gave a robust performance for capturing hydraulic hysteresis behavior in unsaturated flow.

This paper presents an experimental study of the influences of initial major principal stress direction (ξ) and intermediate principal stress coefficient (b) on noncoaxial behavior of soft clay involved pure principal stress rotation. The noncoaxiality discussed in this paper was defined as the difference between the major principal stress direction and the corresponding principal strain increment direction. The results from a series of undrained tests for soft clay consolidated with different initial major principal stress directions (ξ) conducted by a hollow cylinder apparatus (HCA) are presented. The influences of intermediate principal stress coefficient (b) and initial major principal stress direction (ξ) on the variation of noncoaxiality were investigated. The experimental results provided clear evidence for soft clay noncoaxiality–involved cyclic principal stress rotation. The noncoaxiality showed segmentation characteristics. At the beginning of the test, the deviation degrees were also similar in all three tests, equal to approximately 40°. Also, with the same initial major principal stress direction, the degree of noncoaxiality under b = 1 was lower than that under b = 0 and b = 0.5; with the same intermediate principal stress coefficient (b), different variation trends occurred with different initial major principal stress directions. It can be concluded that the degrees of noncoaxiality of clay specimens were affected by both intermediate principal stress coefficient and initial major principal stress direction. The results can provide an experimental basis for constitutive modeling of clays under complex stress path–involved principal stress rotation in future work.

A series of oedometer tests was performed on pure marine clay and sand–marine clay mixtures with various initial water contents in the clay matrix and sand fractions. The hydraulic conductivity was computed from the compressibility and the consolidation curves of the samples. The experimental data indicated that the overall hydraulic conductivity of the mixtures depends on both the initial water content and the sand fraction of the clay matrix at a given stress level. The initial water content of the clay matrix had an influence on the local void ratio, leading to differences in the overall hydraulic conductivity. The influence of the initial water content was substantially reduced for the relationship between the overall hydraulic conductivity and the overall void ratio. A homogenization approach was introduced to estimate the overall hydraulic conductivity that could be determined from the intrinsic permeability parameters of pure marine clay. The proposed model has four parameters, including two intrinsic parameters of the pure marine clay and two additional ones incorporating the evolution of the sand skeleton. The ability of the proposed model to describe the permeability behavior of the sand–marine clay mixtures (and other sand–clay mixtures described in the literature) was verified by use of test data.

Considering the effects of the rotation of the principal stresses, time effects, and wall–back inclination, a new solution for the seismic active failure angle is derived by the pseudodynamic method, according to the total force equilibrium of the sliding soil mass. Through a horizontal differential layer method, new differential equations of the normal seismic active earth pressure and its coefficient for an inclined rigid retaining wall are obtained under translation. Then, using numerical solutions for ordinary differential equations based on the Runge–Kutta method, influences of parameters (i.e., the vibration period time, wall–back inclination, internal friction angle of backfill, wall-soil friction angle, height of wall, amplitude of horizontal, and vertical seismic acceleration coefficient) on the seismic active failure angle are discussed, as well as the seismic active earth pressure and its coefficient. Moreover, the seismic active earth pressures and its coefficients calculated by proposed method are compared with those by existing pseudostatic and pseudodynamic methods. The results showed that the seismic active failure angle, seismic active earth pressure and its coefficient all change periodically with the time, and the distribution of seismic active earth pressure is nonlinear along the wall height. The seismic active earth pressure and its coefficient found in this paper are larger than those found using existing pseudostatic methods.

Ground subsidence and coal gangue induced by mining activities could significantly influence the nearby environment. To allow strict public scrutiny of mining under the metropolitan district, coal gangue backfill has been introduced together with the strip mining method to minimize ground subsidence and to reduce gangue disposal in Tangshan Mine in Hebei Province, China. Field investigation was conducted to evaluate the performances of the combined mining method. The results showed that fractures were primarily generated at distances ranging from 5 m to 85 m behind the longwall face. The majority of fractures occurred within the range of 30 m in the overlying roof strata. The roof strata over the goaf became stable at a distance of 78 m behind the longwall face. The cumulative roof displacement occurred from instrument installation to roof regaining stability was 1084.2 mm. The backfill stresses experienced a slow increase, with a maximum value reaching 0.4 MPa at a distance of 97 m behind the longwall face. The maximum ground subsidence reached 46 mm, which had little impact on nearby buildings. Based upon these findings, it can be concluded that the combination of the backfill technique in strip mining can effectively reduce ground subsidence.

In this article, a practical analytical method for prediction of the postconstruction settlement of high embankments is proposed through the further simplification of the one-dimensional creep deformation algorithm under the theoretical framework of the unified hardening (UH) model. The feasibility and reliability of the proposed practical method were validated by a case study of the Chengde Airport (Chengde city, Hebei province), in which actual settlement measurement data from three monitoring points were employed. The predicted settlement results of the proposed method were further compared with those from two conventional methods, the three-point method and hyperbola method. The results show that the proposed method generally provides a more reliable prediction of settlements over two conventional methods with a limited amount of available measurement data.

This article proposes a graphical method associated with the g line to evaluate seismic slope stability. The g line depicts the combinations of c/γH and tanφ that are necessary to maintain slope stability at the critical limit state. Correlations of c/γH and tanφ are established based on the work-rate balance equation. Under a kinematic analysis, the pseudostatic upper-bound solution of c/γH is sought with an optimization procedure. After having determined the g line, the factor of safety for a specific slope can be easily estimated without the need for iterative calculations. For ease of practical use, a set of stability charts is presented. This approach also permits determination of the critical failure mode, including toe or below the toe.

The theoretical models currently reported in the literature idealize a uniformly tapered pile as a step-tapered pile to facilitate dynamic analysis. The step-taper idealization produces approximate solutions, which become more accurate as the number of steps is increased. This paper presents a new theoretical model for obtaining axial stiffness and damping parameters of tapered piles. The underlying theory is consistent with the traditional elastic model for the vertical vibration of cylindrical piles. The governing differential equation for vertical vibration of a uniformly tapered pile is solved numerically using software, and the dynamic response is analyzed; it is observed that the resonant amplitude can be significantly reduced with an increased taper angle. A simple approximate solution is also presented, and the results are in good agreement with the numerical solution. Frequency-dependent axial stiffness and damping parameters of tapered piles can thus be obtained quickly and with sufficient accuracy by implementation of the proposed approximate method.

The current work investigates the propagation of torsional waves at the interface of a Voigt-type viscoelastic fiber-reinforced layer and a sandy half-space under gravity. The media used are prestressed and heterogeneous. The dispersion relation is established in compact form by the variable separable method. The significant effect of heterogeneity, viscoelasticity, fiber-reinforcement, initial stress, sandiness, and gravity on propagation characteristics of torsional waves has been elucidated graphically. The present work may serve as a helpful tool to connect theoretical results and field applications.

A fractal calculation method was developed to investigate the self-similarity of the time distribution of microseismic events during the evolution of rock bursts. Microseismic data, which were utilized for back-analysis after the rock burst, were collected corresponding to different intensities of immediate rock bursts, occurring in the deeply buried headrace tunnels of Jinping-II Hydropower Station in Sichuan Province, China. The overburden depths of the tunnels are between 1,800 and 2,500 m, where the maximum principal stress reaches 65 MPa in a rock mass mainly comprising Baishan Group marble. The results are as follows: The time distribution of microseismic events during the evolution of immediate rock bursts was found to display fractal properties. If the intensities of rock bursts were lower, the time fractal dimensions were smaller (weak rock bursts < moderate rock bursts < intense rock bursts). The time fractal dimensions can be used as a basis for evaluating rock-burst intensities. Time fractal dimensions correspond to intense rock bursts (>1.6), moderate rock bursts (1.1–1.6), and weak rock bursts (<1.1). The daily time fractal dimensions of microseismic events increased during the process of immediate rock bursts but were significantly reduced before the rock burst occurred. On this basis, the time distribution of microseismic events has the potential to be used as a rock-burst predictor, and the microseismic events time fractal dimension can provide a basis for establishing a warning index and reduce the risk of rock bursts in deep tunnels.

This paper reports theoretical investigations into the behavior of a concrete anchor block embedded in cohesionless soil. This research was carried out for the purpose of devising an analytical method for attaining a reliable and accurate estimate of the pullout capacity of an anchor block embedded at a shallow depth. To this end, it was assumed that a passive wedge of soil developed in front of the anchor block, due to the force exerted from the retaining structure via the attachment to a rebar. The limit equilibrium of the wedge was satisfied, and relevant assumptions were made to idealize the geometry of a failure mechanism. For simplicity in hand calculations, design charts were developed, utilizing the ratio of the breakout factor to the embedment depth to obtain the pullout capacity of an anchor block. The proposed theoretical estimation was compared with existing theoretical and experimental investigations for accuracy and reliability, and the comparison clearly showed the superiority of the proposed method in both the areas. Moreover, the effects of the placement of anchor blocks in relation to retaining structures were studied.